The field of this invention is functional materials useful in optical systems exemplified by, but not limited to, optical switches, modulators, and other devices that are compatible with silica or non-silica waveguides.
A waveguide is any structure which permits the propagation of a wave through its length despite diffractive effects, and possible curvature of the guide structure. An optical waveguide is an optical structure capable of guiding a beam of laser light along light channels in the waveguide, and is defined by an extended region of increased index of refraction relative to the surrounding medium. The waveguide typically includes both the light channels in which light waves propagate in the waveguide, and surrounding cladding which confine the waves in the channel. The strength of the guiding, or the confinement, of the wave depends on the wavelength, the index difference, and the guide width.
Discrete control of the refractive index of a given polymer is necessary for creating silica or non-silica waveguide optical switch components; however, it is not the only property which determines the durability and efficiency required for a commercial product. The present invention demonstrates that there is a critical interplay between the polymer, the silica substrate, the electrodes and the electro-optic material which must be elucidated to create a commercially viable product.
Bosc et al., describes the use of two fluorinated monomers (1H, 1H, 2H, 2H tridecafluoro-octyl methacrylate and trifluoroethyl methacrylate) to create copolymers having refractive index values between 1.370 and 1.403 at 1.3 um (Design and Synthesis of Low Refractive Index Polymers for Modulation in Optical Waveguides, Optical Materials Vol 13 (1999), pp. 205-209). Bosc et al. further discuss copolymerization of an electro-optic monomer, methacrylic acid ester of Disperse Red 1 (the refractive index for a homopolymer of this material is 1.710). These monomers were blended to achieve a final terpolymer refractive index of 1.5. The Tg of these systems varied between 82xc2x0 C. and 92xc2x0 C. While these compositions allow (possess) some degree of optical modulation, they are not suitable for use in an optical switch which meets the reliability and efficiency requirements of commercial communications networks.
These and other deficiencies of the prior art are overcome by the present invention, which provides both polymer systems and electrooptic chromophores that form the components of a optical devices such as optical switches or modulators and other devices useful in an optical waveguide.
The polymer component is a thermoplastic or thermosetting polymer which is blended or co-polymerized with an electrooptic chromophore. The thermoplastic or thermosetting polymer is typically selected from the group consisting of acrylics/methacrylics, polyesters, polyurethanes, polyimides, polyamides, polyphosphazenes, epoxy resins, and hybrid (organic-inorganic) or nanocomposite polyester polymers. Combinations of thermoplastic and thermosetting polymers (interpenetrating polymer networks) are also envisioned as part of this invention.
Additionally, the thermoplastic and/or thermosetting polymer typically has a glass transition temperatures above 100xc2x0 C., one embodiment for low index materials has a refractive index values less-than 1.5 while another embodiment for high index materials has refractive index values greater than 1.5. The polymers are combined with chromophores, either as part of the backbone chain or blended and typically contain compatibilization additives or groups and/or adhesion promotion additives or groups. The electrooptic chromophore according to the invention is typically a substituted aniline, substituted azobenzene, substituted stilbene, or substituted imine with one or more as further defined below.